I've published already quite a few tutorials on greylisting, rbls and so on. Here's another tutorial showing how you can reduce your spam with rather simple means. First of all we need to edit the file /etc/postfix/main.cf and add those lines: smtpd_helo_required = yes strict_rfc821_envelopes = yes disable_vrfy_command = yes unknown_address_reject_code = 554 […]